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Avalanche Forecast

Archived

Dec 9th, 2020–Dec 10th, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.

Regions

Kananaskis.

Watch for windslabs as you transition into open wind affected terrain. Recent natural avalanche activity indicates that these windslabs can also be human triggerred. 

Confidence

High -

Weather Forecast

The storm is over unfortunately! Winds will be light to moderate out of the SW on Thursday as a high pressure system builds back in over the region. Temperatures are expected to cool dramatically with -17C forecast for thursday morning. 

Avalanche Summary

A few sz 2 windslabs were observed failing within the at the interface with the recent storm snow. These were up to 50m across, 40-60cm deep and ran to the top of their normal runouts. A noteable sz 2.5 was observed in the Black Prince area on a NE aspect that ran to the middle of its runout that looked to have entrained some wet snow. Black prince area also had numerous sz 2 avalanches down 15-20cm failing on surface hoar.  

Snowpack Summary

Up to 30cm of snow fell in the past 24hrs with only isolated variable winds in upper elevation. This new snow is overlying a variety of surfaces from surface hoar (up to 2100m) and crusts (solar aspects) that formed in the big warm up last week as well as hard windslabs. Carefully evaluate the bond of this new snow as it begins to strengthen over the next few days. The November crust is down 50-80cm now and continues to produce variable results. The snowpack felt a bit cakey along ridgelines on Wednesday so be watching for winds to increase making these windslabs more reactive. In some areas below 2000m the snowpack was moist...

Terrain and Travel

  • Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.